fetch_impl.hh revision 2831:0a42b294727c
1/* 2 * Copyright (c) 2004-2006 The Regents of The University of Michigan 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions are 7 * met: redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer; 9 * redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution; 12 * neither the name of the copyright holders nor the names of its 13 * contributors may be used to endorse or promote products derived from 14 * this software without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 * 28 * Authors: Kevin Lim 29 * Korey Sewell 30 */ 31 32#include "config/use_checker.hh" 33 34#include "arch/isa_traits.hh" 35#include "arch/utility.hh" 36#include "cpu/checker/cpu.hh" 37#include "cpu/exetrace.hh" 38#include "cpu/o3/fetch.hh" 39#include "mem/packet.hh" 40#include "mem/request.hh" 41#include "sim/byteswap.hh" 42#include "sim/host.hh" 43#include "sim/root.hh" 44 45#if FULL_SYSTEM 46#include "arch/tlb.hh" 47#include "arch/vtophys.hh" 48#include "base/remote_gdb.hh" 49#include "sim/system.hh" 50#endif // FULL_SYSTEM 51 52#include <algorithm> 53 54using namespace std; 55using namespace TheISA; 56 57template<class Impl> 58Tick 59DefaultFetch<Impl>::IcachePort::recvAtomic(PacketPtr pkt) 60{ 61 panic("DefaultFetch doesn't expect recvAtomic callback!"); 62 return curTick; 63} 64 65template<class Impl> 66void 67DefaultFetch<Impl>::IcachePort::recvFunctional(PacketPtr pkt) 68{ 69 panic("DefaultFetch doesn't expect recvFunctional callback!"); 70} 71 72template<class Impl> 73void 74DefaultFetch<Impl>::IcachePort::recvStatusChange(Status status) 75{ 76 if (status == RangeChange) 77 return; 78 79 panic("DefaultFetch doesn't expect recvStatusChange callback!"); 80} 81 82template<class Impl> 83bool 84DefaultFetch<Impl>::IcachePort::recvTiming(Packet *pkt) 85{ 86 fetch->processCacheCompletion(pkt); 87 return true; 88} 89 90template<class Impl> 91void 92DefaultFetch<Impl>::IcachePort::recvRetry() 93{ 94 fetch->recvRetry(); 95} 96 97template<class Impl> 98DefaultFetch<Impl>::DefaultFetch(Params *params) 99 : mem(params->mem), 100 branchPred(params), 101 decodeToFetchDelay(params->decodeToFetchDelay), 102 renameToFetchDelay(params->renameToFetchDelay), 103 iewToFetchDelay(params->iewToFetchDelay), 104 commitToFetchDelay(params->commitToFetchDelay), 105 fetchWidth(params->fetchWidth), 106 cacheBlocked(false), 107 retryPkt(NULL), 108 retryTid(-1), 109 numThreads(params->numberOfThreads), 110 numFetchingThreads(params->smtNumFetchingThreads), 111 interruptPending(false), 112 switchedOut(false) 113{ 114 if (numThreads > Impl::MaxThreads) 115 fatal("numThreads is not a valid value\n"); 116 117 // Set fetch stage's status to inactive. 118 _status = Inactive; 119 120 string policy = params->smtFetchPolicy; 121 122 // Convert string to lowercase 123 std::transform(policy.begin(), policy.end(), policy.begin(), 124 (int(*)(int)) tolower); 125 126 // Figure out fetch policy 127 if (policy == "singlethread") { 128 fetchPolicy = SingleThread; 129 if (numThreads > 1) 130 panic("Invalid Fetch Policy for a SMT workload."); 131 } else if (policy == "roundrobin") { 132 fetchPolicy = RoundRobin; 133 DPRINTF(Fetch, "Fetch policy set to Round Robin\n"); 134 } else if (policy == "branch") { 135 fetchPolicy = Branch; 136 DPRINTF(Fetch, "Fetch policy set to Branch Count\n"); 137 } else if (policy == "iqcount") { 138 fetchPolicy = IQ; 139 DPRINTF(Fetch, "Fetch policy set to IQ count\n"); 140 } else if (policy == "lsqcount") { 141 fetchPolicy = LSQ; 142 DPRINTF(Fetch, "Fetch policy set to LSQ count\n"); 143 } else { 144 fatal("Invalid Fetch Policy. Options Are: {SingleThread," 145 " RoundRobin,LSQcount,IQcount}\n"); 146 } 147 148 // Size of cache block. 149 cacheBlkSize = 64; 150 151 // Create mask to get rid of offset bits. 152 cacheBlkMask = (cacheBlkSize - 1); 153 154 for (int tid=0; tid < numThreads; tid++) { 155 156 fetchStatus[tid] = Running; 157 158 priorityList.push_back(tid); 159 160 memReq[tid] = NULL; 161 162 // Create space to store a cache line. 163 cacheData[tid] = new uint8_t[cacheBlkSize]; 164 165 stalls[tid].decode = 0; 166 stalls[tid].rename = 0; 167 stalls[tid].iew = 0; 168 stalls[tid].commit = 0; 169 } 170 171 // Get the size of an instruction. 172 instSize = sizeof(MachInst); 173} 174 175template <class Impl> 176std::string 177DefaultFetch<Impl>::name() const 178{ 179 return cpu->name() + ".fetch"; 180} 181 182template <class Impl> 183void 184DefaultFetch<Impl>::regStats() 185{ 186 icacheStallCycles 187 .name(name() + ".icacheStallCycles") 188 .desc("Number of cycles fetch is stalled on an Icache miss") 189 .prereq(icacheStallCycles); 190 191 fetchedInsts 192 .name(name() + ".Insts") 193 .desc("Number of instructions fetch has processed") 194 .prereq(fetchedInsts); 195 196 fetchedBranches 197 .name(name() + ".Branches") 198 .desc("Number of branches that fetch encountered") 199 .prereq(fetchedBranches); 200 201 predictedBranches 202 .name(name() + ".predictedBranches") 203 .desc("Number of branches that fetch has predicted taken") 204 .prereq(predictedBranches); 205 206 fetchCycles 207 .name(name() + ".Cycles") 208 .desc("Number of cycles fetch has run and was not squashing or" 209 " blocked") 210 .prereq(fetchCycles); 211 212 fetchSquashCycles 213 .name(name() + ".SquashCycles") 214 .desc("Number of cycles fetch has spent squashing") 215 .prereq(fetchSquashCycles); 216 217 fetchIdleCycles 218 .name(name() + ".IdleCycles") 219 .desc("Number of cycles fetch was idle") 220 .prereq(fetchIdleCycles); 221 222 fetchBlockedCycles 223 .name(name() + ".BlockedCycles") 224 .desc("Number of cycles fetch has spent blocked") 225 .prereq(fetchBlockedCycles); 226 227 fetchedCacheLines 228 .name(name() + ".CacheLines") 229 .desc("Number of cache lines fetched") 230 .prereq(fetchedCacheLines); 231 232 fetchMiscStallCycles 233 .name(name() + ".MiscStallCycles") 234 .desc("Number of cycles fetch has spent waiting on interrupts, or " 235 "bad addresses, or out of MSHRs") 236 .prereq(fetchMiscStallCycles); 237 238 fetchIcacheSquashes 239 .name(name() + ".IcacheSquashes") 240 .desc("Number of outstanding Icache misses that were squashed") 241 .prereq(fetchIcacheSquashes); 242 243 fetchNisnDist 244 .init(/* base value */ 0, 245 /* last value */ fetchWidth, 246 /* bucket size */ 1) 247 .name(name() + ".rateDist") 248 .desc("Number of instructions fetched each cycle (Total)") 249 .flags(Stats::pdf); 250 251 idleRate 252 .name(name() + ".idleRate") 253 .desc("Percent of cycles fetch was idle") 254 .prereq(idleRate); 255 idleRate = fetchIdleCycles * 100 / cpu->numCycles; 256 257 branchRate 258 .name(name() + ".branchRate") 259 .desc("Number of branch fetches per cycle") 260 .flags(Stats::total); 261 branchRate = fetchedBranches / cpu->numCycles; 262 263 fetchRate 264 .name(name() + ".rate") 265 .desc("Number of inst fetches per cycle") 266 .flags(Stats::total); 267 fetchRate = fetchedInsts / cpu->numCycles; 268 269 branchPred.regStats(); 270} 271 272template<class Impl> 273void 274DefaultFetch<Impl>::setCPU(O3CPU *cpu_ptr) 275{ 276 DPRINTF(Fetch, "Setting the CPU pointer.\n"); 277 cpu = cpu_ptr; 278 279 // Name is finally available, so create the port. 280 icachePort = new IcachePort(this); 281 282 Port *mem_dport = mem->getPort(""); 283 icachePort->setPeer(mem_dport); 284 mem_dport->setPeer(icachePort); 285 286#if USE_CHECKER 287 if (cpu->checker) { 288 cpu->checker->setIcachePort(icachePort); 289 } 290#endif 291 292 // Fetch needs to start fetching instructions at the very beginning, 293 // so it must start up in active state. 294 switchToActive(); 295} 296 297template<class Impl> 298void 299DefaultFetch<Impl>::setTimeBuffer(TimeBuffer<TimeStruct> *time_buffer) 300{ 301 DPRINTF(Fetch, "Setting the time buffer pointer.\n"); 302 timeBuffer = time_buffer; 303 304 // Create wires to get information from proper places in time buffer. 305 fromDecode = timeBuffer->getWire(-decodeToFetchDelay); 306 fromRename = timeBuffer->getWire(-renameToFetchDelay); 307 fromIEW = timeBuffer->getWire(-iewToFetchDelay); 308 fromCommit = timeBuffer->getWire(-commitToFetchDelay); 309} 310 311template<class Impl> 312void 313DefaultFetch<Impl>::setActiveThreads(list<unsigned> *at_ptr) 314{ 315 DPRINTF(Fetch, "Setting active threads list pointer.\n"); 316 activeThreads = at_ptr; 317} 318 319template<class Impl> 320void 321DefaultFetch<Impl>::setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr) 322{ 323 DPRINTF(Fetch, "Setting the fetch queue pointer.\n"); 324 fetchQueue = fq_ptr; 325 326 // Create wire to write information to proper place in fetch queue. 327 toDecode = fetchQueue->getWire(0); 328} 329 330template<class Impl> 331void 332DefaultFetch<Impl>::initStage() 333{ 334 // Setup PC and nextPC with initial state. 335 for (int tid = 0; tid < numThreads; tid++) { 336 PC[tid] = cpu->readPC(tid); 337 nextPC[tid] = cpu->readNextPC(tid); 338#if THE_ISA != ALPHA_ISA 339 nextNPC[tid] = cpu->readNextNPC(tid); 340#endif 341 } 342} 343 344template<class Impl> 345void 346DefaultFetch<Impl>::processCacheCompletion(PacketPtr pkt) 347{ 348 unsigned tid = pkt->req->getThreadNum(); 349 350 DPRINTF(Fetch, "[tid:%u] Waking up from cache miss.\n",tid); 351 352 // Only change the status if it's still waiting on the icache access 353 // to return. 354 if (fetchStatus[tid] != IcacheWaitResponse || 355 pkt->req != memReq[tid] || 356 isSwitchedOut()) { 357 ++fetchIcacheSquashes; 358 delete pkt->req; 359 delete pkt; 360 return; 361 } 362 363 // Wake up the CPU (if it went to sleep and was waiting on this completion 364 // event). 365 cpu->wakeCPU(); 366 367 DPRINTF(Activity, "[tid:%u] Activating fetch due to cache completion\n", 368 tid); 369 370 switchToActive(); 371 372 // Only switch to IcacheAccessComplete if we're not stalled as well. 373 if (checkStall(tid)) { 374 fetchStatus[tid] = Blocked; 375 } else { 376 fetchStatus[tid] = IcacheAccessComplete; 377 } 378 379 // Reset the mem req to NULL. 380 delete pkt->req; 381 delete pkt; 382 memReq[tid] = NULL; 383} 384 385template <class Impl> 386void 387DefaultFetch<Impl>::switchOut() 388{ 389 // Fetch is ready to switch out at any time. 390 switchedOut = true; 391 cpu->signalSwitched(); 392} 393 394template <class Impl> 395void 396DefaultFetch<Impl>::doSwitchOut() 397{ 398 // Branch predictor needs to have its state cleared. 399 branchPred.switchOut(); 400} 401 402template <class Impl> 403void 404DefaultFetch<Impl>::takeOverFrom() 405{ 406 // Reset all state 407 for (int i = 0; i < Impl::MaxThreads; ++i) { 408 stalls[i].decode = 0; 409 stalls[i].rename = 0; 410 stalls[i].iew = 0; 411 stalls[i].commit = 0; 412 PC[i] = cpu->readPC(i); 413 nextPC[i] = cpu->readNextPC(i); 414#if THE_ISA != ALPHA_ISA 415 nextNPC[i] = cpu->readNextNPC(i); 416#endif 417 fetchStatus[i] = Running; 418 } 419 numInst = 0; 420 wroteToTimeBuffer = false; 421 _status = Inactive; 422 switchedOut = false; 423 branchPred.takeOverFrom(); 424} 425 426template <class Impl> 427void 428DefaultFetch<Impl>::wakeFromQuiesce() 429{ 430 DPRINTF(Fetch, "Waking up from quiesce\n"); 431 // Hopefully this is safe 432 // @todo: Allow other threads to wake from quiesce. 433 fetchStatus[0] = Running; 434} 435 436template <class Impl> 437inline void 438DefaultFetch<Impl>::switchToActive() 439{ 440 if (_status == Inactive) { 441 DPRINTF(Activity, "Activating stage.\n"); 442 443 cpu->activateStage(O3CPU::FetchIdx); 444 445 _status = Active; 446 } 447} 448 449template <class Impl> 450inline void 451DefaultFetch<Impl>::switchToInactive() 452{ 453 if (_status == Active) { 454 DPRINTF(Activity, "Deactivating stage.\n"); 455 456 cpu->deactivateStage(O3CPU::FetchIdx); 457 458 _status = Inactive; 459 } 460} 461 462template <class Impl> 463bool 464DefaultFetch<Impl>::lookupAndUpdateNextPC(DynInstPtr &inst, Addr &next_PC) 465{ 466 // Do branch prediction check here. 467 // A bit of a misnomer...next_PC is actually the current PC until 468 // this function updates it. 469 bool predict_taken; 470 471 if (!inst->isControl()) { 472 next_PC = next_PC + instSize; 473 inst->setPredTarg(next_PC); 474 return false; 475 } 476 477 predict_taken = branchPred.predict(inst, next_PC, inst->threadNumber); 478 479 ++fetchedBranches; 480 481 if (predict_taken) { 482 ++predictedBranches; 483 } 484 485 return predict_taken; 486} 487 488template <class Impl> 489bool 490DefaultFetch<Impl>::fetchCacheLine(Addr fetch_PC, Fault &ret_fault, unsigned tid) 491{ 492 Fault fault = NoFault; 493 494#if FULL_SYSTEM 495 // Flag to say whether or not address is physical addr. 496 unsigned flags = cpu->inPalMode(fetch_PC) ? PHYSICAL : 0; 497#else 498 unsigned flags = 0; 499#endif // FULL_SYSTEM 500 501 if (cacheBlocked || (interruptPending && flags == 0) || switchedOut) { 502 // Hold off fetch from getting new instructions when: 503 // Cache is blocked, or 504 // while an interrupt is pending and we're not in PAL mode, or 505 // fetch is switched out. 506 return false; 507 } 508 509 // Align the fetch PC so it's at the start of a cache block. 510 fetch_PC = icacheBlockAlignPC(fetch_PC); 511 512 // Setup the memReq to do a read of the first instruction's address. 513 // Set the appropriate read size and flags as well. 514 // Build request here. 515 RequestPtr mem_req = new Request(tid, fetch_PC, cacheBlkSize, flags, 516 fetch_PC, cpu->readCpuId(), tid); 517 518 memReq[tid] = mem_req; 519 520 // Translate the instruction request. 521 fault = cpu->translateInstReq(mem_req, cpu->thread[tid]); 522 523 // In the case of faults, the fetch stage may need to stall and wait 524 // for the ITB miss to be handled. 525 526 // If translation was successful, attempt to read the first 527 // instruction. 528 if (fault == NoFault) { 529#if 0 530 if (cpu->system->memctrl->badaddr(memReq[tid]->paddr) || 531 memReq[tid]->flags & UNCACHEABLE) { 532 DPRINTF(Fetch, "Fetch: Bad address %#x (hopefully on a " 533 "misspeculating path)!", 534 memReq[tid]->paddr); 535 ret_fault = TheISA::genMachineCheckFault(); 536 return false; 537 } 538#endif 539 540 // Build packet here. 541 PacketPtr data_pkt = new Packet(mem_req, 542 Packet::ReadReq, Packet::Broadcast); 543 data_pkt->dataStatic(cacheData[tid]); 544 545 DPRINTF(Fetch, "Fetch: Doing instruction read.\n"); 546 547 fetchedCacheLines++; 548 549 // Now do the timing access to see whether or not the instruction 550 // exists within the cache. 551 if (!icachePort->sendTiming(data_pkt)) { 552 assert(retryPkt == NULL); 553 assert(retryTid == -1); 554 DPRINTF(Fetch, "[tid:%i] Out of MSHRs!\n", tid); 555 fetchStatus[tid] = IcacheWaitRetry; 556 retryPkt = data_pkt; 557 retryTid = tid; 558 cacheBlocked = true; 559 return false; 560 } 561 562 DPRINTF(Fetch, "[tid:%i]: Doing cache access.\n", tid); 563 564 lastIcacheStall[tid] = curTick; 565 566 DPRINTF(Activity, "[tid:%i]: Activity: Waiting on I-cache " 567 "response.\n", tid); 568 569 fetchStatus[tid] = IcacheWaitResponse; 570 } else { 571 delete mem_req; 572 memReq[tid] = NULL; 573 } 574 575 ret_fault = fault; 576 return true; 577} 578 579template <class Impl> 580inline void 581DefaultFetch<Impl>::doSquash(const Addr &new_PC, unsigned tid) 582{ 583 DPRINTF(Fetch, "[tid:%i]: Squashing, setting PC to: %#x.\n", 584 tid, new_PC); 585 586 PC[tid] = new_PC; 587 nextPC[tid] = new_PC + instSize; 588 589 // Clear the icache miss if it's outstanding. 590 if (fetchStatus[tid] == IcacheWaitResponse) { 591 DPRINTF(Fetch, "[tid:%i]: Squashing outstanding Icache miss.\n", 592 tid); 593 memReq[tid] = NULL; 594 } 595 596 // Get rid of the retrying packet if it was from this thread. 597 if (retryTid == tid) { 598 assert(cacheBlocked); 599 cacheBlocked = false; 600 retryTid = -1; 601 retryPkt = NULL; 602 delete retryPkt->req; 603 delete retryPkt; 604 } 605 606 fetchStatus[tid] = Squashing; 607 608 ++fetchSquashCycles; 609} 610 611template<class Impl> 612void 613DefaultFetch<Impl>::squashFromDecode(const Addr &new_PC, 614 const InstSeqNum &seq_num, 615 unsigned tid) 616{ 617 DPRINTF(Fetch, "[tid:%i]: Squashing from decode.\n",tid); 618 619 doSquash(new_PC, tid); 620 621 // Tell the CPU to remove any instructions that are in flight between 622 // fetch and decode. 623 cpu->removeInstsUntil(seq_num, tid); 624} 625 626template<class Impl> 627bool 628DefaultFetch<Impl>::checkStall(unsigned tid) const 629{ 630 bool ret_val = false; 631 632 if (cpu->contextSwitch) { 633 DPRINTF(Fetch,"[tid:%i]: Stalling for a context switch.\n",tid); 634 ret_val = true; 635 } else if (stalls[tid].decode) { 636 DPRINTF(Fetch,"[tid:%i]: Stall from Decode stage detected.\n",tid); 637 ret_val = true; 638 } else if (stalls[tid].rename) { 639 DPRINTF(Fetch,"[tid:%i]: Stall from Rename stage detected.\n",tid); 640 ret_val = true; 641 } else if (stalls[tid].iew) { 642 DPRINTF(Fetch,"[tid:%i]: Stall from IEW stage detected.\n",tid); 643 ret_val = true; 644 } else if (stalls[tid].commit) { 645 DPRINTF(Fetch,"[tid:%i]: Stall from Commit stage detected.\n",tid); 646 ret_val = true; 647 } 648 649 return ret_val; 650} 651 652template<class Impl> 653typename DefaultFetch<Impl>::FetchStatus 654DefaultFetch<Impl>::updateFetchStatus() 655{ 656 //Check Running 657 list<unsigned>::iterator threads = (*activeThreads).begin(); 658 659 while (threads != (*activeThreads).end()) { 660 661 unsigned tid = *threads++; 662 663 if (fetchStatus[tid] == Running || 664 fetchStatus[tid] == Squashing || 665 fetchStatus[tid] == IcacheAccessComplete) { 666 667 if (_status == Inactive) { 668 DPRINTF(Activity, "[tid:%i]: Activating stage.\n",tid); 669 670 if (fetchStatus[tid] == IcacheAccessComplete) { 671 DPRINTF(Activity, "[tid:%i]: Activating fetch due to cache" 672 "completion\n",tid); 673 } 674 675 cpu->activateStage(O3CPU::FetchIdx); 676 } 677 678 return Active; 679 } 680 } 681 682 // Stage is switching from active to inactive, notify CPU of it. 683 if (_status == Active) { 684 DPRINTF(Activity, "Deactivating stage.\n"); 685 686 cpu->deactivateStage(O3CPU::FetchIdx); 687 } 688 689 return Inactive; 690} 691 692template <class Impl> 693void 694DefaultFetch<Impl>::squash(const Addr &new_PC, unsigned tid) 695{ 696 DPRINTF(Fetch, "[tid:%u]: Squash from commit.\n",tid); 697 698 doSquash(new_PC, tid); 699 700 // Tell the CPU to remove any instructions that are not in the ROB. 701 cpu->removeInstsNotInROB(tid); 702} 703 704template <class Impl> 705void 706DefaultFetch<Impl>::tick() 707{ 708 list<unsigned>::iterator threads = (*activeThreads).begin(); 709 bool status_change = false; 710 711 wroteToTimeBuffer = false; 712 713 while (threads != (*activeThreads).end()) { 714 unsigned tid = *threads++; 715 716 // Check the signals for each thread to determine the proper status 717 // for each thread. 718 bool updated_status = checkSignalsAndUpdate(tid); 719 status_change = status_change || updated_status; 720 } 721 722 DPRINTF(Fetch, "Running stage.\n"); 723 724 // Reset the number of the instruction we're fetching. 725 numInst = 0; 726 727#if FULL_SYSTEM 728 if (fromCommit->commitInfo[0].interruptPending) { 729 interruptPending = true; 730 } 731 732 if (fromCommit->commitInfo[0].clearInterrupt) { 733 interruptPending = false; 734 } 735#endif 736 737 for (threadFetched = 0; threadFetched < numFetchingThreads; 738 threadFetched++) { 739 // Fetch each of the actively fetching threads. 740 fetch(status_change); 741 } 742 743 // Record number of instructions fetched this cycle for distribution. 744 fetchNisnDist.sample(numInst); 745 746 if (status_change) { 747 // Change the fetch stage status if there was a status change. 748 _status = updateFetchStatus(); 749 } 750 751 // If there was activity this cycle, inform the CPU of it. 752 if (wroteToTimeBuffer || cpu->contextSwitch) { 753 DPRINTF(Activity, "Activity this cycle.\n"); 754 755 cpu->activityThisCycle(); 756 } 757} 758 759template <class Impl> 760bool 761DefaultFetch<Impl>::checkSignalsAndUpdate(unsigned tid) 762{ 763 // Update the per thread stall statuses. 764 if (fromDecode->decodeBlock[tid]) { 765 stalls[tid].decode = true; 766 } 767 768 if (fromDecode->decodeUnblock[tid]) { 769 assert(stalls[tid].decode); 770 assert(!fromDecode->decodeBlock[tid]); 771 stalls[tid].decode = false; 772 } 773 774 if (fromRename->renameBlock[tid]) { 775 stalls[tid].rename = true; 776 } 777 778 if (fromRename->renameUnblock[tid]) { 779 assert(stalls[tid].rename); 780 assert(!fromRename->renameBlock[tid]); 781 stalls[tid].rename = false; 782 } 783 784 if (fromIEW->iewBlock[tid]) { 785 stalls[tid].iew = true; 786 } 787 788 if (fromIEW->iewUnblock[tid]) { 789 assert(stalls[tid].iew); 790 assert(!fromIEW->iewBlock[tid]); 791 stalls[tid].iew = false; 792 } 793 794 if (fromCommit->commitBlock[tid]) { 795 stalls[tid].commit = true; 796 } 797 798 if (fromCommit->commitUnblock[tid]) { 799 assert(stalls[tid].commit); 800 assert(!fromCommit->commitBlock[tid]); 801 stalls[tid].commit = false; 802 } 803 804 // Check squash signals from commit. 805 if (fromCommit->commitInfo[tid].squash) { 806 807 DPRINTF(Fetch, "[tid:%u]: Squashing instructions due to squash " 808 "from commit.\n",tid); 809 810 // In any case, squash. 811 squash(fromCommit->commitInfo[tid].nextPC,tid); 812 813 // Also check if there's a mispredict that happened. 814 if (fromCommit->commitInfo[tid].branchMispredict) { 815 branchPred.squash(fromCommit->commitInfo[tid].doneSeqNum, 816 fromCommit->commitInfo[tid].nextPC, 817 fromCommit->commitInfo[tid].branchTaken, 818 tid); 819 } else { 820 branchPred.squash(fromCommit->commitInfo[tid].doneSeqNum, 821 tid); 822 } 823 824 return true; 825 } else if (fromCommit->commitInfo[tid].doneSeqNum) { 826 // Update the branch predictor if it wasn't a squashed instruction 827 // that was broadcasted. 828 branchPred.update(fromCommit->commitInfo[tid].doneSeqNum, tid); 829 } 830 831 // Check ROB squash signals from commit. 832 if (fromCommit->commitInfo[tid].robSquashing) { 833 DPRINTF(Fetch, "[tid:%u]: ROB is still squashing.\n", tid); 834 835 // Continue to squash. 836 fetchStatus[tid] = Squashing; 837 838 return true; 839 } 840 841 // Check squash signals from decode. 842 if (fromDecode->decodeInfo[tid].squash) { 843 DPRINTF(Fetch, "[tid:%u]: Squashing instructions due to squash " 844 "from decode.\n",tid); 845 846 // Update the branch predictor. 847 if (fromDecode->decodeInfo[tid].branchMispredict) { 848 branchPred.squash(fromDecode->decodeInfo[tid].doneSeqNum, 849 fromDecode->decodeInfo[tid].nextPC, 850 fromDecode->decodeInfo[tid].branchTaken, 851 tid); 852 } else { 853 branchPred.squash(fromDecode->decodeInfo[tid].doneSeqNum, 854 tid); 855 } 856 857 if (fetchStatus[tid] != Squashing) { 858 // Squash unless we're already squashing 859 squashFromDecode(fromDecode->decodeInfo[tid].nextPC, 860 fromDecode->decodeInfo[tid].doneSeqNum, 861 tid); 862 863 return true; 864 } 865 } 866 867 if (checkStall(tid) && fetchStatus[tid] != IcacheWaitResponse) { 868 DPRINTF(Fetch, "[tid:%i]: Setting to blocked\n",tid); 869 870 fetchStatus[tid] = Blocked; 871 872 return true; 873 } 874 875 if (fetchStatus[tid] == Blocked || 876 fetchStatus[tid] == Squashing) { 877 // Switch status to running if fetch isn't being told to block or 878 // squash this cycle. 879 DPRINTF(Fetch, "[tid:%i]: Done squashing, switching to running.\n", 880 tid); 881 882 fetchStatus[tid] = Running; 883 884 return true; 885 } 886 887 // If we've reached this point, we have not gotten any signals that 888 // cause fetch to change its status. Fetch remains the same as before. 889 return false; 890} 891 892template<class Impl> 893void 894DefaultFetch<Impl>::fetch(bool &status_change) 895{ 896 ////////////////////////////////////////// 897 // Start actual fetch 898 ////////////////////////////////////////// 899 int tid = getFetchingThread(fetchPolicy); 900 901 if (tid == -1) { 902 DPRINTF(Fetch,"There are no more threads available to fetch from.\n"); 903 904 // Breaks looping condition in tick() 905 threadFetched = numFetchingThreads; 906 return; 907 } 908 909 DPRINTF(Fetch, "Attempting to fetch from [tid:%i]\n", tid); 910 911 // The current PC. 912 Addr &fetch_PC = PC[tid]; 913 914 // Fault code for memory access. 915 Fault fault = NoFault; 916 917 // If returning from the delay of a cache miss, then update the status 918 // to running, otherwise do the cache access. Possibly move this up 919 // to tick() function. 920 if (fetchStatus[tid] == IcacheAccessComplete) { 921 DPRINTF(Fetch, "[tid:%i]: Icache miss is complete.\n", 922 tid); 923 924 fetchStatus[tid] = Running; 925 status_change = true; 926 } else if (fetchStatus[tid] == Running) { 927 DPRINTF(Fetch, "[tid:%i]: Attempting to translate and read " 928 "instruction, starting at PC %08p.\n", 929 tid, fetch_PC); 930 931 bool fetch_success = fetchCacheLine(fetch_PC, fault, tid); 932 if (!fetch_success) { 933 if (cacheBlocked) { 934 ++icacheStallCycles; 935 } else { 936 ++fetchMiscStallCycles; 937 } 938 return; 939 } 940 } else { 941 if (fetchStatus[tid] == Idle) { 942 ++fetchIdleCycles; 943 } else if (fetchStatus[tid] == Blocked) { 944 ++fetchBlockedCycles; 945 } else if (fetchStatus[tid] == Squashing) { 946 ++fetchSquashCycles; 947 } else if (fetchStatus[tid] == IcacheWaitResponse) { 948 ++icacheStallCycles; 949 } 950 951 // Status is Idle, Squashing, Blocked, or IcacheWaitResponse, so 952 // fetch should do nothing. 953 return; 954 } 955 956 ++fetchCycles; 957 958 // If we had a stall due to an icache miss, then return. 959 if (fetchStatus[tid] == IcacheWaitResponse) { 960 ++icacheStallCycles; 961 status_change = true; 962 return; 963 } 964 965 Addr next_PC = fetch_PC; 966 InstSeqNum inst_seq; 967 MachInst inst; 968 ExtMachInst ext_inst; 969 // @todo: Fix this hack. 970 unsigned offset = (fetch_PC & cacheBlkMask) & ~3; 971 972 if (fault == NoFault) { 973 // If the read of the first instruction was successful, then grab the 974 // instructions from the rest of the cache line and put them into the 975 // queue heading to decode. 976 977 DPRINTF(Fetch, "[tid:%i]: Adding instructions to queue to " 978 "decode.\n",tid); 979 980 // Need to keep track of whether or not a predicted branch 981 // ended this fetch block. 982 bool predicted_branch = false; 983 984 for (; 985 offset < cacheBlkSize && 986 numInst < fetchWidth && 987 !predicted_branch; 988 ++numInst) { 989 990 // Get a sequence number. 991 inst_seq = cpu->getAndIncrementInstSeq(); 992 993 // Make sure this is a valid index. 994 assert(offset <= cacheBlkSize - instSize); 995 996 // Get the instruction from the array of the cache line. 997 inst = gtoh(*reinterpret_cast<MachInst *> 998 (&cacheData[tid][offset])); 999 1000 ext_inst = TheISA::makeExtMI(inst, fetch_PC); 1001 1002 // Create a new DynInst from the instruction fetched. 1003 DynInstPtr instruction = new DynInst(ext_inst, fetch_PC, 1004 next_PC, 1005 inst_seq, cpu); 1006 instruction->setTid(tid); 1007 1008 instruction->setASID(tid); 1009 1010 instruction->setThreadState(cpu->thread[tid]); 1011 1012 DPRINTF(Fetch, "[tid:%i]: Instruction PC %#x created " 1013 "[sn:%lli]\n", 1014 tid, instruction->readPC(), inst_seq); 1015 1016 DPRINTF(Fetch, "[tid:%i]: Instruction is: %s\n", 1017 tid, instruction->staticInst->disassemble(fetch_PC)); 1018 1019 instruction->traceData = 1020 Trace::getInstRecord(curTick, cpu->tcBase(tid), cpu, 1021 instruction->staticInst, 1022 instruction->readPC(),tid); 1023 1024 predicted_branch = lookupAndUpdateNextPC(instruction, next_PC); 1025 1026 // Add instruction to the CPU's list of instructions. 1027 instruction->setInstListIt(cpu->addInst(instruction)); 1028 1029 // Write the instruction to the first slot in the queue 1030 // that heads to decode. 1031 toDecode->insts[numInst] = instruction; 1032 1033 toDecode->size++; 1034 1035 // Increment stat of fetched instructions. 1036 ++fetchedInsts; 1037 1038 // Move to the next instruction, unless we have a branch. 1039 fetch_PC = next_PC; 1040 1041 if (instruction->isQuiesce()) { 1042 warn("cycle %lli: Quiesce instruction encountered, halting fetch!", 1043 curTick); 1044 fetchStatus[tid] = QuiescePending; 1045 ++numInst; 1046 status_change = true; 1047 break; 1048 } 1049 1050 offset+= instSize; 1051 } 1052 } 1053 1054 if (numInst > 0) { 1055 wroteToTimeBuffer = true; 1056 } 1057 1058 // Now that fetching is completed, update the PC to signify what the next 1059 // cycle will be. 1060 if (fault == NoFault) { 1061 DPRINTF(Fetch, "[tid:%i]: Setting PC to %08p.\n",tid, next_PC); 1062 1063#if THE_ISA == ALPHA_ISA 1064 PC[tid] = next_PC; 1065 nextPC[tid] = next_PC + instSize; 1066#else 1067 PC[tid] = next_PC; 1068 nextPC[tid] = next_PC + instSize; 1069 nextPC[tid] = next_PC + instSize; 1070 1071 thread->setNextPC(thread->readNextNPC()); 1072 thread->setNextNPC(thread->readNextNPC() + sizeof(MachInst)); 1073#endif 1074 } else { 1075 // We shouldn't be in an icache miss and also have a fault (an ITB 1076 // miss) 1077 if (fetchStatus[tid] == IcacheWaitResponse) { 1078 panic("Fetch should have exited prior to this!"); 1079 } 1080 1081 // Send the fault to commit. This thread will not do anything 1082 // until commit handles the fault. The only other way it can 1083 // wake up is if a squash comes along and changes the PC. 1084#if FULL_SYSTEM 1085 assert(numInst != fetchWidth); 1086 // Get a sequence number. 1087 inst_seq = cpu->getAndIncrementInstSeq(); 1088 // We will use a nop in order to carry the fault. 1089 ext_inst = TheISA::NoopMachInst; 1090 1091 // Create a new DynInst from the dummy nop. 1092 DynInstPtr instruction = new DynInst(ext_inst, fetch_PC, 1093 next_PC, 1094 inst_seq, cpu); 1095 instruction->setPredTarg(next_PC + instSize); 1096 instruction->setTid(tid); 1097 1098 instruction->setASID(tid); 1099 1100 instruction->setThreadState(cpu->thread[tid]); 1101 1102 instruction->traceData = NULL; 1103 1104 instruction->setInstListIt(cpu->addInst(instruction)); 1105 1106 instruction->fault = fault; 1107 1108 toDecode->insts[numInst] = instruction; 1109 toDecode->size++; 1110 1111 DPRINTF(Fetch, "[tid:%i]: Blocked, need to handle the trap.\n",tid); 1112 1113 fetchStatus[tid] = TrapPending; 1114 status_change = true; 1115 1116 warn("cycle %lli: fault (%d) detected @ PC %08p", curTick, fault, PC[tid]); 1117#else // !FULL_SYSTEM 1118 warn("cycle %lli: fault (%d) detected @ PC %08p", curTick, fault, PC[tid]); 1119#endif // FULL_SYSTEM 1120 } 1121} 1122 1123template<class Impl> 1124void 1125DefaultFetch<Impl>::recvRetry() 1126{ 1127 assert(cacheBlocked); 1128 if (retryPkt != NULL) { 1129 assert(retryTid != -1); 1130 assert(fetchStatus[retryTid] == IcacheWaitRetry); 1131 1132 if (icachePort->sendTiming(retryPkt)) { 1133 fetchStatus[retryTid] = IcacheWaitResponse; 1134 retryPkt = NULL; 1135 retryTid = -1; 1136 cacheBlocked = false; 1137 } 1138 } else { 1139 assert(retryTid == -1); 1140 // Access has been squashed since it was sent out. Just clear 1141 // the cache being blocked. 1142 cacheBlocked = false; 1143 } 1144} 1145 1146/////////////////////////////////////// 1147// // 1148// SMT FETCH POLICY MAINTAINED HERE // 1149// // 1150/////////////////////////////////////// 1151template<class Impl> 1152int 1153DefaultFetch<Impl>::getFetchingThread(FetchPriority &fetch_priority) 1154{ 1155 if (numThreads > 1) { 1156 switch (fetch_priority) { 1157 1158 case SingleThread: 1159 return 0; 1160 1161 case RoundRobin: 1162 return roundRobin(); 1163 1164 case IQ: 1165 return iqCount(); 1166 1167 case LSQ: 1168 return lsqCount(); 1169 1170 case Branch: 1171 return branchCount(); 1172 1173 default: 1174 return -1; 1175 } 1176 } else { 1177 int tid = *((*activeThreads).begin()); 1178 1179 if (fetchStatus[tid] == Running || 1180 fetchStatus[tid] == IcacheAccessComplete || 1181 fetchStatus[tid] == Idle) { 1182 return tid; 1183 } else { 1184 return -1; 1185 } 1186 } 1187 1188} 1189 1190 1191template<class Impl> 1192int 1193DefaultFetch<Impl>::roundRobin() 1194{ 1195 list<unsigned>::iterator pri_iter = priorityList.begin(); 1196 list<unsigned>::iterator end = priorityList.end(); 1197 1198 int high_pri; 1199 1200 while (pri_iter != end) { 1201 high_pri = *pri_iter; 1202 1203 assert(high_pri <= numThreads); 1204 1205 if (fetchStatus[high_pri] == Running || 1206 fetchStatus[high_pri] == IcacheAccessComplete || 1207 fetchStatus[high_pri] == Idle) { 1208 1209 priorityList.erase(pri_iter); 1210 priorityList.push_back(high_pri); 1211 1212 return high_pri; 1213 } 1214 1215 pri_iter++; 1216 } 1217 1218 return -1; 1219} 1220 1221template<class Impl> 1222int 1223DefaultFetch<Impl>::iqCount() 1224{ 1225 priority_queue<unsigned> PQ; 1226 1227 list<unsigned>::iterator threads = (*activeThreads).begin(); 1228 1229 while (threads != (*activeThreads).end()) { 1230 unsigned tid = *threads++; 1231 1232 PQ.push(fromIEW->iewInfo[tid].iqCount); 1233 } 1234 1235 while (!PQ.empty()) { 1236 1237 unsigned high_pri = PQ.top(); 1238 1239 if (fetchStatus[high_pri] == Running || 1240 fetchStatus[high_pri] == IcacheAccessComplete || 1241 fetchStatus[high_pri] == Idle) 1242 return high_pri; 1243 else 1244 PQ.pop(); 1245 1246 } 1247 1248 return -1; 1249} 1250 1251template<class Impl> 1252int 1253DefaultFetch<Impl>::lsqCount() 1254{ 1255 priority_queue<unsigned> PQ; 1256 1257 1258 list<unsigned>::iterator threads = (*activeThreads).begin(); 1259 1260 while (threads != (*activeThreads).end()) { 1261 unsigned tid = *threads++; 1262 1263 PQ.push(fromIEW->iewInfo[tid].ldstqCount); 1264 } 1265 1266 while (!PQ.empty()) { 1267 1268 unsigned high_pri = PQ.top(); 1269 1270 if (fetchStatus[high_pri] == Running || 1271 fetchStatus[high_pri] == IcacheAccessComplete || 1272 fetchStatus[high_pri] == Idle) 1273 return high_pri; 1274 else 1275 PQ.pop(); 1276 1277 } 1278 1279 return -1; 1280} 1281 1282template<class Impl> 1283int 1284DefaultFetch<Impl>::branchCount() 1285{ 1286 list<unsigned>::iterator threads = (*activeThreads).begin(); 1287 panic("Branch Count Fetch policy unimplemented\n"); 1288 return *threads; 1289} 1290